HomeMy WebLinkAbout504 S WHITCOMB STREET, CARRIAGE HOUSE - FDP210006 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE RELATED DOCUMENT504 S. Whitcomb Street
DRAINAGE SUMMARY
Design Engineer:
Design Firm:
Project Number:
Date:
IMPERVIOUS SUMMARY:
Description Basin Area
(sqft)
Roof Area
(sqft)
Gravel Area
(sqft)
Total
Impervious
Area (sqft)
%
Impervious
100-yr Peak
Runoff Rate
(cfs)
Existing 5,818 761
723 1,484 27.9% 0.56
Proposed 5,357 648 1,006 1,654 28.8% 0.52
Difference -461 -113 283 170 0.9% -0.04
A.McKenna
Highland Development Services
21-1039-00
November 15, 2021
This table is to document the existing and proposed impervious areas, percent impervious, and
associated peak runoff rates, related to the areas draining to the alley from 504 S. Whitcomb St.
504 S. Whitcomb St - Rational Calcs.xlsx Page 1 of 5 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
%
Impervious
Runoff
Coefficient C
Return
Period
Frequency
Adjustment
Factor (Cf)
100% 0.95
2-year to
10-year 1.00
90% 0.95 100-year 1.25
90% 0.95
40% 0.50
15% 0.35
* Lawn area assumed to be 15% imperv and 0.35 coeff to account for misc walks
C2 to C10 C100
Ex Alley 22,098 0.507 718 3,458 0 1,958 15,964 31.7% 0.48 0.60
Ex 504 5,818 0.134 0 761 0 723 4,334 27.9% 0.45 0.56
Prop 504 5,357 0.123 0 648 0 1,006 3,703 28.8% 0.45 0.56
Weighted %
Impervious
COMPOSITEApaved
(sq feet)
Aroof
(sq feet)
Awalk
(sq feet)
Agravel/pavers
(sq feet)
Alawn
(sq feet)
Gravel/Pavers
Lawns*
(Clayey, Flat < 2% Slope)
Sub-basin
Designation
Atotal
(sq feet)
Atotal
(acres)
% Impervious values from Table 3.2.2 in the Fort Collins Stormwater Criteria Manual
Land Use
Paved
Roof
Walks
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
504 S. Whitcomb Street
DEVELOPED IMPERVIOUS AREA CALCULATION
DESIGN CRITERIA:
Fort Collins Stormwater Criteria Manual
BASINS:
A.McKenna
Highland Development Services
21-1039-00
November 15, 2021
504 S. Whitcomb St - Rational Calcs.xlsx Page 2 of 5 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 5-3 -Equation 5-4 -Urbanized Check Equation 3.3-5
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (2-yr to 10-yr)
Ex Alley Ex Alley 31.7% 0.48 0.507 191 0.0063 18.79 24 0.0078 0.14 0.025 1.42 0.28 19.07 215 11.19 11.19
Ex 504 Ex 504 27.9% 0.45 0.134 150 0.0047 19.24 13 0.0174 0.14 0.025 2.12 0.10 19.34 163 10.90 10.90
Prop 504 Prop 504 28.8% 0.45 0.123 70 0.0076 11.11 101 0.0040 0.14 0.025 1.02 1.65 12.76 170 10.95 10.95
OVERALL LENGTH
(ft/ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
LENGTH
(ft)
SLOPE
(ft/ft)
VELOCITY
(ft/s)
ROUGHNESS
COEFFICIENT
HYDRAULIC
RADIUS
(ft)
LENGTH
(ft)
DESIGN CRITERIA:
City of Fort Collins Stormwater Criteria Manual
Overland Flow Equations for City of Fort Collins Stormwater Criteria Manual
SUB-BASIN DATA INITIAL/OVERLAND
TIME (ti)TRAVEL TIME (tt)
tc=ti+tt
(min)
Urban Check Final
tc
(min)DESIGN
POINT Sub-basin %
Impervious C2-10
AREA
(acres)
tt
(min)
November 15, 2021
504 S. Whitcomb Street
DEVELOPED TIME OF CONCENTRATION
A.McKenna
21-1039-00
Highland Development Services
ticttt+=
V
Ltt60
=1.871.1
10
180
+=LtcV.R2/3 S 1/2
504 S. Whitcomb St - Rational Calcs.xlsx Page 3 of 5 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:
-Equation 5-3 -Equation 5-4 -Urbanized Check Equation 3.3-5
- CoFC Overland Flow
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
Time of Concentration (100-yr)
Ex Alley Ex Alley 31.7% 0.60 0.507 191 0.0063 15.20 24 0.0078 0.14 0.025 1.42 0.28 15.48 215 11.19 11.19
Ex 504 Ex 504 27.9% 0.56 0.134 150 0.0047 15.95 13 0.0174 0.14 0.025 2.12 0.10 16.04 163 10.90 10.90
Prop 504 Prop 504 28.8% 0.56 0.123 70 0.0076 9.18 101 0.0040 0.14 0.025 1.02 1.65 10.83 170 10.95 10.83
OVERALL LENGTH
(ft/ft)
tc
(min)
SLOPE
(ft/ft)
ti
(min)
LENGTH
(ft)
SLOPE
(ft/ft)
VELOCITY
(ft/s)
HYDRAULIC
RADIUS
(ft)
ROUGHNESS
COEFFICIENT
LENGTH
(ft)
DESIGN CRITERIA:
City of Fort Collins Stormwater Criteria Manual
Overland Flow Equations for City of Fort Collins Stormwater Criteria Manual
SUB-BASIN DATA INITIAL/OVERLAND
TIME (ti)TRAVEL TIME (tt)
tc=ti+tt
(min)
Urban Check Final
tc
(min)DESIGN
POINT Sub-basin %
Impervious C100
AREA
(acres)
tt
(min)
November 15, 2021
504 S. Whitcomb Street
DEVELOPED TIME OF CONCENTRATION
A.McKenna
21-1039-00
Highland Development Services
ticttt+=
V
Ltt60
=1.871.1
10
180
+=LtcV.R2/3 S 1/2
504 S. Whitcomb St - Rational Calcs.xlsx Page 4 of 5 Highland Development Services
Design Engineer:
Design Firm:
Project Number:
Date:
EQUATIONS:I = rainfall intensity (in/hr)
Q n = n -yr peak discharge (cfs)P 1 = one-hour point rainfall depth (in)
C n = n -yr runoff coefficient t c = time of concentration (min)
I n = n -yr rainfall intensity (in/hr) P 1-2yr =0.82 in
A n = Basin drainage area (ac)P 1-10yr =1.40 in
P 1-100yr 2.86 in
BASIN SUMMARY:
tc (min)
Runoff
Coeff
(C2-10)
C(A)
(acres)
Intensity
(in/hr)
Q2
(ft3/s)
tc (min)
Runoff
Coeff
(C2-10)
C(A)
(acres)
Intensity
(in/hr)
Q10
(ft3/s)
tc (min)
Runoff
Coeff
(C100)
C(A) (acres)Intensity
(in/hr)
Q100
(ft3/s)
Ex Alley Ex Alley 0.507 31.7% 11.19 0.48 0.24 2.12 0.51 11.19 0.48 0.24 3.61 0.87 11.19 0.60 0.30 7.38 2.24
Ex 504 Ex 504 0.134 27.9% 10.90 0.45 0.06 2.14 0.13 10.90 0.45 0.06 3.65 0.22 10.90 0.56 0.07 7.46 0.56
Prop 504 Prop 504 0.123 28.8% 10.95 0.45 0.06 2.14 0.12 10.95 0.45 0.06 3.65 0.20 10.83 0.56 0.07 7.48 0.52
10-yr Peak Runoff 100-yr Peak Runoff
504 S. Whitcomb Street
DEVELOPED PEAK RUNOFF
DESIGN CRITERIA:
Design
Point Sub-basin Area
(acres)
A.McKenna
Highland Development Services
21-1039-00
July 1, 2021
2-yr Peak Runoff
City of Fort Collins Stormwater Criteria Manual
%
Impervious
nnnnAICQ=
(0.786651)
1
)10(
5.28
ct
PI
+
=
504 S. Whitcomb St - Rational Calcs.xlsx Page 5 of 5 Highland Development Services